1. Field of the Invention
This invention relates generally to the field of reverse osmosis by the passage of solutes across a membrane, and more specifically, to altering the relative concentrations of solvent to solute in a solution.
2. Description of the Prior Art
Reverse osmosis is not new. In its simplest terms, it is the passage of a solvent from a solution which is under pressure across a semi-permeable membrane which tends to block the solute.
The most common applications of reverse osmosis are in areas such as sea water desalination and blood purification (artificial kidney machine). Efforts to improve such applications have generally been directed to finding membranes which totally block a particular solute or to cascading systems which compensate for the failure of a membrane to totally block a solute.
The use of countercurrent flow in reverse osmosis devices and cascading is evidenced in, for example, U.S. Pat. Nos. 3,799,873, 2,930,754 and 3,276,997.
Efforts to find such an ideal membrane have not been greatly successful. Reverse osmosis devices which use currently available membranes and cascading systems often require undesirably high pressures and numerous cascading steps to obtain acceptably high concentrations of solvent.
A system for altering the concentration of solvent to solute in a solution which avoids the necessity of extremely high pressures and multiple cascading steps is desirable. Such a system which avoids the need for a membrane capable of totally blocking the solute is also desirable.